National report of LITHUANIA THE 4th BALTIC SURVEYORS FORUM, 2013, Ventspils, LATVIA Eimuntas Parseliunas Geodetic Institute of Vilnius Technical University Transition to European Vertical Reference System – EVRS: Status of the geodetic vertical control of Lithuania and further movements

Outline General ideas World Geodetic Vertical Datum and System Local (European) Vertical Reference System National Geodetic Vertical Network Further movements

General ideas Approaches for the construction and unification of Geodetic Vertical Reference Systems and Frames: Spirit leveling Gravity field Marker of the vertical reference frame Physical height difference Ellipsoidal height difference and geoid model Benchmark Precise levelings and gravimetric observations (leveling approach) GNSS (gravity field approach) Tide gaugeOceanographic modelSatellite altimetry

Ellipsoidal height, orthometric height, local geoid, vertical datum... General ideas

Geopotential number Dynamic height Orthometric height Nominal value of gravity at mid-latitude Average value of gravity along the plumb line Normal height Average value of normal gravity along the normal plumb line m 2 s -2

General ideas As there is a similar problem for the uncertainty in the topographic density distribution in determining orthometric heights (but not for normal heights), we conclude that a normal height system is the best choice for a future height system. Once the normal gravity field is defined, the normal heights and the quasigeoid can be determined without any error stemming from the topographic mass distribution, and the quasigeoid can be estimated more precisely than the geoid as the reference surface. L. E. Sjöberg. The geoid or quasigeoid – which reference surface should be preferred for a national height system? Journal of Geodetic Science, 3(2), 2013,

World Geodetic Vertical Datum and System

Different teams computed W 0 using the same input data, but their own methodologies: Input data Mean sea surface models (MSS): CLS11 (Schaeffer et al. 2012) DTU10 (Andersen 2010) Global gravity models (GGM): EGM2008 (Pavlis et al, 2012) EIGEN6C (Förste et al. 2011) GOCO3S (Mayer-Gürr et al. 2012)

World Geodetic Vertical Datum and System Some examples of W 0 estimates

World Geodetic Vertical Datum and System The reference level W 0 for potential differences can arbitrarily be appointed. However, to get the worldwide consistency desired within a global vertical reference system, the selected W 0 value must be realisable with high-precision at any time and anywhere around the world. Therefore, it is necessary to estimate it from real observations of the Earth's gravity field and surface. The uniqueness, reliability and repeatability of the global reference level W 0 (or global geoid) can only be guaranteed by introducing specific conventions (like any other reference system!). On the contrary, there will exist as many height systems as W 0 computations. Remarks on W 0

World Geodetic Vertical Datum and System All the computations are delivering very close results (around m 2 s -2 ), but there are still differences of about 0,5 m 2 s -2 (~ 5 cm). It is necessary to start defining the standards and conventions for a formal recommendation on W 0. Final recommendation (till the end of 2013): ,0 +/- 0,2 m 2 s -2 But... Canada: November 2013, CGVD2013 with ,0 m 2 s -2 USA till 2020 also with ,0 m 2 s -2

World Geodetic Vertical Datum and System (EGM96)

World Geodetic Vertical Datum and System Project „Investigations of the requirements for a future 5 mm (quasi)geoid model“ has recently been started within the Nordic Geodetic Commission (NKG). The NKG gravity database will soon be updated in connection with the NKG-project „Computation of the NKG2014 geoid model“.

Local (European) Vertical Reference System Spirit leveling Approach EVRF2007

Local (European) Vertical Reference System

Spirit leveling approach Transformation parameter Estimation of 3 parameters (plane) as transformation parameters between the national vertical reference frames and EVRF2007

Local (European) Vertical Reference System

National Geodetic Vertical Network (1) Lithuanian vertical (height) system is still not adopted. The project of The Resolution of the Government of Lithuania is prepared! It is based on EVRS Conventions 2007.

National Geodetic Vertical Network (1) 10 datum points

National Geodetic Vertical Network (1) Data of datum points

National Geodetic Vertical Network (1)

National Geodetic Vertical Network (3)

National Geodetic Vertical Network (11)

National Geodetic Vertical Network (12)

National Geodetic Vertical Network (13)

National Geodetic Vertical Network (14) Differences between some height systems

National Geodetic Vertical Network (14) Precise levelling in (in green) and near future plans (in red)

Vertical network (1st and 2nd order)

Red lines – foreseen 2nd order lines

Vertical network - numbers Total lenght of lines – 3100 km: Ready km (in 2007) km (in 2012) Foreseen – 2200 km (in ) Characteristics of projected 2nd order Network Total number of points (new –2800)

Lithuanian state geodetic vertival network fits to the requirements of the modern society It necessary to speed up the adoption of the Vertical (height) and Gravity systems in Lithuania The densification of the first order vertical network should be executed to fulfill the all needs of the geodesy science Conclusions

Adoption of vertical (height) and gravity systems – 2013 Quasigeoid model (2 cm) NKG GNSS campaign – 2013 LitPOS modernization – Second order vertical network – Absolute gravity measurements at Vilnius, Panevezys and Klaipeda – 2013 Gravity survey – GNSS campaign at vertical network points Quasigeoid model (5mm) Future plans

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